The subject matter disclosed herein relates to a filter unit for adjusting the energy spectrum of X-ray, as well as an X-ray tube unit and an X-ray imaging system both having the filter unit. Particularly, the embodiments described herein are concerned with a filter unit of low cost permitting replacement of plural filters, as well as an X-ray tube unit and an X-ray imaging system.
In an X-ray imaging system, X-ray is radiated to a subject after adjusting its energy spectrum with a filter. The filter is installed within a collimator box attached to an X-ray tube. In the invention of Japanese Unexamined Patent Publication No. 2006-226985, for obtaining a desired spectrum, the filter can be used by switching from one to another among plural filter plates secured to a rotary disc.
For radiating X-ray to a standing subject or to a subject who is lying down, it is necessary for an X-ray tube unit to direct its angle in an arbitrary direction. To meet this requirement it is necessary to reduce the size of the X-ray tube unit. An X-ray irradiation unit disclosed in the above-referenced patent publication permits adjustment in multiple stages, but the size of an X-ray tube unit used is large. Besides, if the X-ray tube unit is provided with plural drive devices such as motors, it becomes complicated in structure and gets out of order more frequently, with an increase of the manufacturing cost.
Accordingly, it is desirable to provide a filter unit simple in structure and small in size, as well as an X-ray tube unit and an X-ray imaging system both having the filter unit.